IB Chemistry HL Structure 3 Classification of Matter Questions

Practise IB Chemistry HL Structure 3 with reviewed questions on periodicity, transition elements, organic structure, spectroscopy and matter classification.

Exam points

Use periodic position and electron configuration to compare elements and predict chemical behaviour.
Explain periodic trends, group reactivity, oxide character, oxidation states and transition-element behaviour using chemical evidence.
Deduce organic structures, formulae and IUPAC names from connectivity, functional-group and reaction evidence.
Classify homologous series and structural isomers, then relate branching, polarity and intermolecular forces to physical properties.
Use mass spectrometry, infrared and proton NMR data, including splitting patterns, to identify organic structures.

Covered syllabus points

3.1 The periodic table 3.2 Functional groups: Organic compounds

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Study Structure 3. Classification of matter conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

[Maximum number: 5]

Lithium and boron are elements in period 2 of the periodic table. Lithium occurs in group 1 (the alkali metals) and boron occurs in group 3. Isotopes exist for both elements.

(a)

Distinguish between the terms group and period.

[ 1 ]

(b)

State the other most common ion of cobalt.

[ 1 ]

$\mathrm{Co}^{2+}$ ;

Marking guidance:

Accept +2, 2+, cobalt(II), II.

(c)

Explain why the complex $\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right] \mathrm{Cl}_{3}$ is coloured.

[ 3 ]

[Maximum number: 2]

(a)

An organic compound, X, with a molar mass of approximately $88 \mathrm{~g} \mathrm{~mol}^{-1}$ contains 54.5 % carbon, 36.3 % oxygen and 9.2 % hydrogen by mass.

[ 2 ]

(i)

X is a straight-chain carboxylic acid. Draw its structural formula.

[ 1 ]

$\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{COOH}$ ;

(ii)

Draw the structural formula of an isomer of X which is an ester.

[ 1 ]

$\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COOCH}_{3} / \mathrm{CH}_{3} \mathrm{COOCH}_{2} \mathrm{CH}_{3} / \mathrm{HCOOCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3} / \mathrm{HCOOCH}\left(\mathrm{CH}_{3}\right)_{2}$ ;

[Maximum number: 6]

Iron rusts in the presence of oxygen and water. Rusting is a redox process involving several steps that produces hydrated iron(III) oxide, $\mathrm{Fe}_{2} \mathrm{O}_{3} \bullet \mathrm{nH}_{2} \mathrm{O}$ , as the final product. The half-equations involved for the first step of rusting are given below.

Half-equation 1: $\quad \mathrm{Fe}(\mathrm{s}) \rightarrow \mathrm{Fe}^{2+}(\mathrm{aq})+2 \mathrm{e}^{-}$

Half-equation 2: $\quad \mathrm{O}_{2}(\mathrm{aq})+4 \mathrm{e}^{-}+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow 4 \mathrm{OH}^{-}(\mathrm{aq})$

(a)

Identify the oxidation number of each atom in the three species in half-equation 2.

Figure for Question (a) — IB Chemistry HL

[ 2 ]

$\mathrm{O}_{2}(aq)+4e^{-}+2\mathrm{H}_{2}\mathrm{O}(l) \rightarrow 4\mathrm{OH}^{-}(aq)$

Oxidation numbers:

Species/atom	Oxidation number
O in $\mathrm{O}_{2}$	0
H in $\mathrm{H}_{2}\mathrm{O}$	+I
O in $\mathrm{H}_{2}\mathrm{O}$	-II
O in $\mathrm{OH}^{-}$	-II
H in $\mathrm{OH}^{-}$	+I

Species/atom	Oxidation number
O in $\mathrm{O}_{2}$	0
H in $\mathrm{H}_{2}\mathrm{O}$	+I
O in $\mathrm{H}_{2}\mathrm{O}$	-II
O in $\mathrm{OH}^{-}$	-II
H in $\mathrm{OH}^{-}$	+I

(b)

State the relationship between the electron arrangement of an element and its group and period in the periodic table.

[ 2 ]

(c)

Transition metals and their compounds often catalyse reactions. The catalyzed decomposition of hydrogen peroxide by CuO is an example. State two other examples of catalyzed reactions giving the transition metal or its compound acting as catalyst.

[ 2 ]

$\quad \mathrm{V}_{2} \mathrm{O}_{5}$ catalyses oxidation of $\mathrm{SO}_{2}$ / $\mathrm{V}_{2} \mathrm{O}_{5}$ is a catalyst in the Contact Process; Fe catalyses the reaction between $\mathrm{N}_{2}$ and $\mathrm{H}_{2}$ / Fe is a catalyst in the Haber Process; $\mathrm{Ni} / \mathrm{Pd} / \mathrm{Pt}$ catalyses hydrogenation / manufacture of margarine / addition of hydrogen to C=C / conversion of alkenes to alkanes;\n $\mathrm{Pd} / \mathrm{Pt}$ is a catalyst in catalytic converters / $\mathrm{Pd} / \mathrm{Pt}$ catalyzes reaction of $\mathrm{NO}_{2}$ and $\mathrm{CO}$ / $\mathrm{NO}_{2}$ and (unburnt) fuel/exhaust gases;

[Maximum number: 9]

Organic compounds have many industrial applications.

(a)

The following organic compound, X, is used as a flavouring agent.

[ 5 ]

(i)

State the name of the functional group present in X.

[ 1 ]

(ii)

Deduce the systematic name of X using IUPAC nomenclature.

[ 1 ]

(iii)

Deduce the number of signals and their relative areas (integration traces) in an ${ }^{1} \mathrm{H}$ NMR spectrum of X.

Number of signals:
Relative areas:

[ 2 ]

(iv)

Draw an isomer of X which belongs to a different homologous series.

[ 1 ]

Figure for Answer to Question (iv) — IB Chemistry HL

OR

Accept any ketone, unsaturated alcohol/ether or cyclic alcohol/ether, with molecular formula $\mathrm{C}_{9} \mathrm{H}_{18} \mathrm{O}$ .

Accept any correct representation including skeletal structures.

Ignore connectivity of methyl groups

(b)

An alkene such as ethene can be used as starting material for a range of compounds.

[ 1 ]

(i)

State the general formula for the homologous series of alkenes.

[ 1 ]

$\mathrm{C}_{\mathrm{n}} \mathrm{H}_{2 \mathrm{n}}$

Subscripts of numbers not
essential

(c)

The chloroalkene with the formula $\mathrm{C}_{4} \mathrm{H}_{7} \mathrm{Cl}$ can exist as several stereoisomers.

[ 3 ]

(i)

Draw the structural formula of cis-1-chlorobut-2-ene.

[ 1 ]

(ii)

Deduce the structure of a chloroalkene, $\mathrm{C}_{4} \mathrm{H}_{7} \mathrm{Cl}$ , that can exhibit optical isomerism, and identify the chiral carbon atom with an asterisk (*).

[ 2 ]

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